Enhancing the Schedulability of Real-Time Heterogeneous Networks of Workstations (NOWs)

This paper proposes a realtime duplication based algorithm (RT-DBA) for scheduling precedence-related periodic tasks with hard deadlines on networks of workstations (NOWs). We have utilized selective subtask duplication that enables some tasks to have earlier start times, which enables additional tasks (and, hence, task sets) to finish before their deadlines, thereby increasing the schedulability of a real-time application. We strongly believe that duplication can be used as a tool for obtaining a better quality of service (QoS) from the real-time heterogeneous system, and this is our major contribution. We have taken both the computation and the communication heterogeneities into account while modeling such a system. Both data and control dependencies between the tasks have also been considered. Our algorithm exhibits scalability, fully exploits the underlying parallelism, and is capable of scheduling an application, even if the available number of processors is less than the required number of processors. Based on extensive simulation studies, we observe that RT-DBA offers an enhanced success ratio as compared to other scheduling schemes when communication is a dominant factor.